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Cognitive Neuroscience Lecture 15: Attention 1
L15: Attention 1 What is Attention? William James: - Selection: Choosing 1 possibility out of many - Withdrawal: ignoring the rest Many definitions - Filtering, Selecting, Binding, Focusing, Enhancing Basic characteristics - Limited capacity o Can only attend to a subset of visual input (some of space, a few objs) o Multiple object tracking: we go bad after approx. 4-5 objs o This requires selection: what/how to select, what results? - Selection o Consequences of attentional selection § Inattentional blindness: Moonwalking bear § Selective reading: if you’re told to read only a certain type of text, you will unless something pops out at you like your name, special words like sex, physically different stim like caps/numbers, or stuff relating to the topic to main focus of attention (bold green example) - Modulation o Once selected, attention can enhance visual perception and neural responses o Attention alters the contrast sensitivity § If given a cue on a particular side, you notice more contrast on that side - Vigilance o ability to sustain attention over time o person seeks to detect appearance of a particular target stim of interest o Long lasting tasks: e.g. airport scanner, where’s waldo Our definition of attention: - Process by which one or a few among many competing representations are selected for prioritized representation - Mechanism '''that controls perception and information being perceived - Alters neural activity, giving stronger responses to attended info and weaker to unattended info - Occurs across many cortical regions (even subcortical), across all domains (sensory/motor/higher cognition) When does attentional selection (aka filtering) happen? - In both early and late selection: o Stimulusà o Sensory registrationà o Semantic processingà o Response - '''Early selection: selection before semantic processing o we have a limited capacity to process information and we only select a small subset of this information for extensive processing o Bottleneck is BEFORE SEMANTIC PROCESSING o You only process SOME inputs o Evidence: § Dichotic listening task; only reported stream attended to · What breaks through? Sensory information. ''' o Switch to pure tone o Switch gender · What doesn’t break through? '''Semantic information. o Switch languages o Played backwards § Differences in EEG brain waves based on attention as early as 100ms o Problems with Early selection: § “Cocktail Party Effect”: even if you’re not attending to a convo, you’ll hear if they say your name (and understanding your name is semantic info) § Some info can break through: your name and “fire” § Stroop Effect: can’t filter out meaning of words - Late selection: selection after semantic processing o both attended and ignored inputs are processed equivalently by the perceptual system, reaching stages of semantic encoding and analysis o Bottleneck is AFTER SEMANTIC PROCESSING ''' o AFTER you process it, you only respond to some - Basically, there’s evidence for both. - '''The determining factor may be “attentional load”: how demanding is the task o Low-load/easy: late selection § None of them is hard, so you have more resources to spread and don’t need to filter any out o High-load/requiring lots of resources: early selection § You have less to focus on then Irony of Load and Selection - Sometimes, under low-load you can be more distracted since information can ‘break through’ - Easy task: bad performance, “easily distracted” - Hard task: good performance, “difficult to distract” William James on Attention: “depends on…'what '''the things are.” What are the units of attention? What do we select? - '''Space' o Spatial orienting: Posner cuing task § Valid: cue pointed in direction of target § Invalid: cue pointed away from target § Neutral: cue pointed in both directions o Covert attention: attention without eye movements o Overt attention: attention through eye movements o Results of Posner cuing task: RT is shorter when you shift your attention first o 2 ways to selectively orient attention: § Endogenous attention '''(goal directed) · Voluntary · Top-down § '''Exogenous attention (stimulus driven) · Reflexive · Bottom-up o Posner cuing ARROW is based on endogenous (look for the thing the arrow is pointing to…goal directed) o Posner cuing BOLDING is based on exogenous (no one tells you to focus on the bolded square, but you do it) o Deficit in attending to space: spatial neglect § Following damage to dorsal pathway (parietal, usually right) § Loss of attention or awareness to contralesional side (usually left side) § Neglect on the left visual space § Inferior parietal lobule & TPJ are important for space-centered, exogenous attention ''' § o '''Neural Mechanisms: Parietal neurons and attention § Monkey fixating passively § Monkey not attendingànot much firing in parietal neurons · Monkey makes an eye movement, big response from parietal neurons (even before eye-movement occurs) · Overt attention: he’s moving his eyes § Covert attention · Monkey makes a hand movementà big response even though eyes never move · Covert attention: no saccades, just reaching o What are these parietal activations doing? § Modulating activity in other visual areas: TPJ affecting other regions § Attention alters the contrast sensitivity o Attention modulates the activity of V4 neurons § What will happen to V4 neuron response when both stimuli are presented within the receptive field of the cell? § Depends on which object the monkey is attending to § Monkey ignoring display, just paying attention to fixation · Cell responds strongly to blue-vertical alone but not white alone · Response of neuron “biased” towards attended stimulus (increased when effective stimulus, decreased when ineffective stimulus) · V4 responds more to effective ' o '''Cue period: endogenous attention ' o '''Target period: exogenous attention o Attention & Parietal lobe, § Parietal dissociation: different parts for exogenous vs endogenous · Intraparietal sulcus/superior parietal lobule: '''endogenous, cue-related orienting, goal-directed · '''Temporoparietal junction/inferior parietal lobule: exogenous, target detection, stimulus-driven o 'Dual Network Theory ' § Dorsal attention network helps orient attention in a goal-directed manner § Ventral attention network detects salient stimuli and triggers reorienting to them o 'Dorsal attention network: domain general shifting '(shows that any goal-oriented uses dorsal): GOAL DIRECTED; DORSAL § Shift task between magnitude and parity § Shift location between left and right § Same IPS/SPL regions mediate shifting spatial attention and task sets